Power amplifier



June 23, 1942.

G; BARTH 2,287,755

POWER AMPLIFIER Filed April 26, 1940 fj l' Ii INVENTOR.

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? ATTORNEY.

netization curve.

Patented June 23, 1942 POWER AMPLIFIER Gustav Barth, Berlin, Germany,assignor to'Siemens Apparate nnd Maschinen Gesellscliaft mitbeschrankter Hai'tnng, Berlin, Germany, a cor- -poratln of GermanyApplication April 26, 1940, Serial No. 331,874

In Germany November 30, 1938 7 Claims. (Cl. 171-242) This inventionrelates to an arrangement for adjusting an organ, particularly a controlsurface or the like in airplanes or seagoing vessels.

In the copending application Serial No. 290,968

filed August 19, 1939, is described an arrange-- ment for adjusting anorgan, particularly a control surface or the like in airplanes orseagoing vessels in accordance with instruments capable of being loadedonly to a slight extent, such as directional indicators, for instance,compasses, gyro-indicators or the like.

According to the above copending application the electrical magnitudetransmitted by said instruments is transmitted to a magnetic amplifierarrangement connected to a feed back circuit and is amplified by theamplifier arrangement in such a manner that the output energy which theamplifier supplies to the current consuming device,'for instance, to anelectrical directional drive, has such a value as to bring about anadjustment of the organ.

The present invention relates to an improvement in the novel magneticamplifier provided invention the operation of the magnetic amplifierdisclosed in the above copending application is hereinafter brieflyrepeated with reference to Figs. 1 and 2.

In Fig. l, I and 2 denote cores consisting of a material of highmagnetic permeability, for instance, of an'iron-nickel alloy. The twocores are provided each with a winding 3 and 4 respectively. The twowindings 3 and 4 are arranged in series and in series withthe currentconsuming device 5 energized by the altematingcurrent source 6. In thewindings and therefore in the current consuming device S'flows analternating current J whose magnitude depends upon thealternating-current resistance of the windings. The magnitude of thisresistance depends upon the permeability of the two cores in accordancewith the working point on the maga common winding I which is traversedby the direct current is supplied byan impulse transmitter (not shown).The two windings 3 and 4 are so wound that the voltages induced in theing the working point the permeability changes.

On the two cores is arranged according to the magnetization curve andthere- I fore changes the alternating-current resistance of the windingsland 4. The alternating-current resistance of these windings dependstherefore upon the direct current is flowing 'in the winding I andvaries with the direct current.

If the output current is plotted against the input current in a diagramfor an arrangement according to Fig. 1 without consuming device, theinclination of the tangent on this curve in the working point is to beconsidered as the steepness of the magnetic amplifier. The amplificationfactor of the arrangement'depends upon this steepness.

In the arrangement according to the above copending application anincrease of the amplification factor is attained by the fact that thealternating current flowing in the windings 3 and 4 is rectified and isrendered effective in the sense of a self-amplification by the feed backby supplying the alternating current to an additional winding which isallotted to the two cores in the same manner as the winding 1 of Fig. 1.The effect of this feed back will now be briefly explained with thereference to Fig. 2 in connection with the disclosure of the abovecopending application. In Fig. 2 the same parts are denoted by. the samereference numerals as in Fig. 1. I and 2 denote the cores consisting ofa material of highmagnetic permeability, 3 and 4 the windings arrangedon these cores and traversed by the alternating current, 5 the currentconsuming device and 6 the power source. I designates the windingtraversed by the direct current supplied by the directional indicator 8.The alternating current flowing in the windings 3 and 4 traverses arectifier arrangement 9. The current rectified with the aid of thisrectifier arrangement is supplied to the additional winding III which isallotted to the cores I and 2 in the same manner as the winding 1.Consequently, a periodically variable current whose effect may beattributed to the effect of a direct current flows in the winding Ill.The current in this winding displaces the working point on themagnetization curve and therefore varies the permeability of the cores Iand 2 as well as the alternating-current resistance of the windings 3and 4 in the same manner as above described for the effect of thecurrent ie flowing in the winding I. of flow of the current in therectifier arrangement 9 and upon the direction of the current flowing inthe winding 1 the current in the winding I0 produces in the cores l and2 mag- Depending upon the direction 1 netic fluxes which have botheither the same or.

opposite direction as the fluxes which are produced by the current is inthe winding 1, i. e., the fluxes may be either added or subtracted. Itis first assumed that is=0. The current J flowing in the windings 3 and4 and in the current consuming device 5 is denoted in this case by Joand the current flowing in the winding I0 is denoted by 7'0correspondingly to the zero current Jo. The working point on themagnetization curve of the cores 1 and 2 is determined by the currentsJo and 7'0. If a current is flows in the winding 1 in the direction thatthe magnetic fluxes in the cores produced thereby have the samedirection as the fluxes which are produced by 7, the working point onthe magnetization curve is shifted by the effect of the current is so asto reduce the permeability of the cores and therefore thealternating-current resistance of the two windings 3 and 4. Withdecreasing alternating-current resistance J increases, which in turnbrings about an increase of '7. To the increase of 9' corresponds anincrease of the flux in the cores produced by-this current, whichincrease causes a further decrease ofthe permeability, therefore afurther decrease of the alternating-current resistances of the windings3 and 4 as well a a further increase of the cur- .rent J. Consequently,the current 7' causes an increase in the effect of the input current, isin the form of a self-amplification and therefore an increase in theamplification factor.

In this arrangement the feed back is constant. The magnitude of the feedback and therefore the amplification factor cannot assume any high valuefor the following reason. The resistance of the two windings 3 and 4retains always a definite value also in case the winding 1 isdeenergized, i. e. an alternating current flows in this arrangement alsoin this zero position. This zero current Jo produces a magnetic bias andthereby decreases the initial permeability as well as the initialresistance of the windings 3 and 4. This means an undesirable increasein the zero current with increasing number of turns of the winding Itwith respect to an arrangement without feed back and at the same time arestriction of the controllable resistance range of the windings 3 and4, since the smallest resistance value which these windings may assumeis the value for which the two cores l and 2 are completely saturated.Upon these two moments with increasing current is the number of the.

depends the selection of the magnitudeof the constant feed back.

According to the present invention means are provided in the feed backcircuit for preferably automatically controlling the feed back so as toinfluence the amplification factor.

Further details of the invention will be apparent from the followingdescription taken in connection with the accompanying drawing, in

which 1 Figs. 1 and 2 diagrammatically show the mag netic amplifierdescribed in the above copending application. 7

Fig. 3 shows an embodiment of the novel arrangement in which theeffective number of turns of the feed back winding may be varied.

Figs. 4 and 5 show further embodiments of the invention in whichregulable resistances are em-.

ployed.

Fig. 6 shows an embodiment of the invention with two impulsetransmitters serving as regulating organs. I

In Fig. 3, in which are diagrammatically illustrated the parts shown inFig. 2, I and 2 denote the two cores, 3 and 4 the windings traversed bythe alternating current J, 5 the current consuming device, 6 thealternating-current source,.1 the winding traversed by the input currentin and 8 the impulse transmitter supplying the input current. The feedback winding I0 is on the one hand directly connected to the rectifierarrangement 9 and on the other hand through a. slide contact II. Theslide contact is operated by an instrument I! operating in thisembodiment in the form of a measuring mechanism and which is traversedby the current is. The slide contact causes depending upon its positionmore or less turns of the feed back winding 10 to be traversed by therectified alternating current so as to increase more or less the feedback. In this case the arrangement is so designed that for an inputcurrent 1 12 0 no or only a few turns of the winding III are inserted inthe circuit, that turns inserted increases and that for the maximumvalue of the input current is the desired greatest number of feed backwindings lie in the feed back circuit.

If the input current is very small, the effect of the feed back is veryslight. The effect may be reduced to a minimum, which implies that thezero current in the arrangement may be reduced to an output value as isdesired for an arrangement without feed back. In this manner at the sametime the complete controllable resistance range of the windings 3 and 4is maintained as in the case of the arrangement without feed back. It isnow thus possible to give the feed back for the greatest value of is andtherefore the amplification factor of the magnetic amplifier any highvalue.

Fig. 4 shows another embodiment of the invention. The arrangement of theparts 1 to 6 and 9 is the same as that shown in the embodiment of Fig. 3and is therefore not shown in this figure. In Fig. 4 the feed backwinding I0 is connected to the points a and b of Fig. 3 and the numberof turns of the winding I0 is so chosen that for the maximum value of isthe desired maximum feed back is atained. Parallel to this feed backwinding is connected a resistance l3 whose effective magnitude iscontrollable in accordance with the intensity of the input current iswith the aid of the slide contact H operated by the instrument It. Inthis case the arrangement is, for instance, so designed that for themaximum value of is the slide contact ll lies on the free end of theresistance which is so chosen that in this'case it is practicallyineffective as a shunt for the winding l0, whereas for is==0 the slidecontact H lies on the opposite end of the resistance l3 and the windingI0 is thus practically short circuited and therefore the feed back isineffective.

In Fig. 5 the resistance I4 is series connected to-the feed back windingand is controlled in a similar manner as in the embodiment shown in Fig.4 by the instrument I! with the aid of the slide contact II, in whichcase, however, the resistance l4 for is=0 assumes its maximum value iskept large for small input currents ie and small for large inputcurrents ie.

According to the invention it is also possible to control the feed backby hand alone or in connection with the automatic control. The automaticcontrol may be controlled by the input current or also by an auxiliarycurrent alone or in connection with the input current which is suppliedby another impulse transmitter. Such an embodiment is shown in Fig. 6 inwhich l denotes a double instrument whichis operated on the one hand bythe input current ie and on the other hand by the auxiliary current izsupplied by the impulse transmitter l6.

Of course, any electrical magnitudes supplied by the impulsetransmitters may be employed for the control.

What is claimed is: I

l. A magnetic amplifier comprising .a magnetizable core carrying a pairof windings connected in series opposed relation, a source ofalternating current connected to energize said pair of windings, meansfor rectifyingihe output current of said windings, a direct currentinput circuit including a third winding on said core whereby duringcurrent flow in said third winding the reactance and output current ofsaid pair of windings are varied, feed back means for said core foradditionally varying the reactance of said pair of windings inaccordance with the output current of the rectifying means, and controlmeans electrically connected with said feed back means and saidrectifying means and energized pair of windings, means for rectifyingthe output current of said windings, a direct current input circuitincluding a third winding on said core whereby during current flow insaid third winding the reactance and output current of-said pair ofwindings is varied, feed back means comprising a fourth winding wound onsaid core and connected with said rectified output current foradditionally varying the reactance and output current of said pair ofwindings in accordance with the output current of the rectifying means,and control means electrically connected with said feed back means andsaid rectifying means and energized by the current flowing in the direct current input circuit for controlling the effect of said fourthwinding on said core as a function of the current flowing in said..direc current circuit.

, 4. A magnetic amplifier comprising a mag? netizable core carrying apair of coils connectedin series opposed relation, a source ofalternating current connected to energize said pair of coils, means forrectifying the output current of said coils, a direct current inputcircuit including a third coil on said corewhereby during current fiowin said third coil the reactance and output current of said pair ofcoils is varied, feed back means including a fourth coil having aplurality of turns mounted on said core and connected,

with said rectified output current whereby current flows therethrough toadditionally vary the reactance and output current of said pair ofcoils, resistance means in circuit with said fourth coil,

. and means energized by theAcurrent flowing in by the currentfiowing inthe direct current input circuit for controlling the effect of said feedback means on said core as a function of the current flowing in saiddirect current input circuit.

2. A magnetic amplifier comprising a magnetizable core carrying a pairof windings connected in series opposed relation, a source ofalternating current connected to energize saidoutput current of saidpair of windings in accord ance with the output current of therectifying means, and control means electrically connected with saidfeed back 'means and said rectifying means and energized by the currentflowing in the direct current input circuit for controlling the effectof said feed back means on said core as a function of the currentflowing in said direct current circuit. r

3. A magnetic amplifier comprising a magnetizabie core carrying a pairof windings connected in series opposed relation, a source ofalternating current connected to energize said the third coil andassociated with said feed back means for engaging and variably selectingthe value of said resistance means whereby the effect of said fourthcoil upon said pair of coils is 'varied as a function of the inputcurrent of said third winding.

5. A magnetic amplifier comprising a mag netizable core carrying a pairof coils connected in series opposed relation, a source of alternatingcurrent connected to energize said pair of coils, means for rectifyingthe output current of said coils, adirect current input circuitincluding a third coil on said core whereby duringv current How in saidthird coil the reactance and output current of said pair of coils isvaried, feed back means including a fourth coil having a plurality ofturns mounted on said core and connected with said rectified outputcurrent whereby current flows therethrough to additionally vary thereactanceand output current of said pair of coils, resistance means incircuit with said fourth coil, and control means actuated in accordancewith the direct current fiow in said third coil for slld ably engagingand variably selecting the value of said resistance means whereby theeffect of said fourth coil upon saidpair of coils is varied as afunction of the ing.

6. A magnetic amplifier comprising a mag-.

input current of said third wind-.

the reactance and output current of said pair of windings, a resistorinparallel with said fourth winding, and means slidably engaging saidresistor for variably selecting the value of said resistor in accordancewith the value of current flowing in said third winding whereby thecurrent flow in 1 function of said input current.

said fourthwindingis controlled as a cuit including a third winding onsaid core where- 5 by during current flow in said third winding thereactance and output current of said pair of windings is varied, feedback means including a fourth windingon said core and connected with 5said rectifying means output whereby current fiow's i'risaid fourthwinding to additionally vary the reactance and output current of saidpair of windings, a resistor in series with said fourth winding, andmeans slidably engaging said re- 10 sistor for variably selecting thevalue of said re-- sistor inaccordance with the value of current flowingin said third winding whereby the current flow in said fourth winding iscontrolled as a function of said input current.

, GUSTAV BARTH.

